I currently have a 2008 6.4 powerstroke which I love! It's a supercab short bed (extended cab). Things have changed a bit in life and I want to lower my payment and possibly look into a crew cab. I was looking at 6.0 and 7.3 powerstrokes and found some nice ones but I used to havering a pretty fast truck (mines tuned and deleted with the hd300 tune). The 6.0 and 7.3 are dogs compared to my 6.4, I started looking at duramax's. What years are the best to look at? I'd like to stay 03 and newer and not to big of a fan of the 07.5+ body style so I guess 03-07 trucks. I really like the gmc sierra but seems like the silverado's are easier to come by? So I guess my questions are which years are the most realizable? Which are the most fuel efficient? And easiest/ cheapest to mod and make fast? How many miles is too many miles and what should I pay for one with 150k miles or less crew cab and extended cab? What are the basic modifications to start with? This may be a dumb question on a gm forum but will I be happy with a duramax over my 6.4 powerstroke? Thanks for all the help and sorry for my grammar I'm on my iPhone.